FTP Client not working behind router

Hi all. I use FTP a lot, and have never experienced this issue. A client has a firewall that they needed to whitelist me for, but when I try to connect, I just time out. So I bypassed my router, and can connect no problem (I'm using ADSL, PPPoE). Can anyone give me clues where to start looking to address this issue and get back behind my router?

I'm using a D-Link DIR-655. Do I need to port forward 21 to my individual computer or something? The server is FTP, not SFTP, running on port 21, and I think they are hosted at hosting.com, or at least that is where their firewall is.